Anticorrosive



Patented d 30, 1945 ANTICOBROSIVE Frederick T. Weiss, Normandy, Mm, assignor to Shell Development Company, San Francisco, Calif., a corporation 02 Delaware No Drawing. Application February 9, 1943, Serial No. 475,305

1 Claim.

The present invention relates to compositions having anti-corrosive, and especially rust-protective, properties, and more particularly deals with compositions comprising a substantially neutral vehicle, such as normally liquid or normally solid hydrocarbons, esters, e. e., fatty oils and natural waxes, etc., containing finely dispersed small amounts of free alkyl malonlc acids having at least 16 carbon atoms.

Metallic surfaces, particularly those containing iron, require protection against the hazard of corrosion in the presence of 'water. To illustrate: Moisture readily attacks finished or semi-finished metal objects unless the metal surface is covered during storage or shipment by a protective coating such as a slushing oil; water in Diesel engine fuels often corrodes closely fitted parts such as are found in Diesel engine unit type injectors; water in turbines corrodes turbine lubricant circulatory systems, particularly the governor mechanisms of steam turbines; and water in hydrocarbon oils such as gasoline rusts steel storage tanks and drums. Corrosion not only has a deleterious effect upon the metal surfaces, but also frequently loosens finely divided metal oxides which may act as oxidation catalysts increasing the rate of deterioration of various organic compounds with which they come in contact or may enter between moving parts of machiner where they act as abrasives.

It is a purpose of this invention to produce potent corrosion-protective compositions of wide applicability. A specific purpose is to produce rust-protective hydrocarbon compositions. i. e.. including various Diesel oils, steam turbine oils, reases, etc.

It is known that many dicarboxylic acids of relatively high molecular weights have anti-corrosive properties, notably the alkyl succinic acids, when dissolved in small quantities in hydrocarbon oils and the like. Alkyl malonic acids, however, have not been employed in anti-corrosive lubricants because it is well known that malonic acids are very unstable, easily losing CO2 and thereby being converted to monocarboxylic acids which have little, if any, anti-corrosive properties.

Now I have discovered that, contrary to ex pectations, the high molecular weight alkyl malonic acids of 16 and more carbon atoms are stable up to about 300 F., provided they are present in concentrations not above about .1%. Stability up to 300 F. is ample for practically any lubricating purpose other than for internal combustion engines. In particular, it is sufficient for steam turbine oils, the problem of corrosion being particularly severe in steam turbines.

Accordingly, my invention comprises corrosionpreventative hydrocarbon oils which, durin their useful lives, are never heated to above 300 F. Such oils should be well refined and be substantially free from as'phalts, resins and gummy materials, such as petroleum resins, asphalts, etc., since these substances greatly reduce the susceptibility of the hydrocarbon oils toward the i5, corrosion-protective properties of the alkyl malonic acids. Oils of poor inhibitor susceptibility containing .1% or less of the malonic acids might not give the desired protection.

Oils of my invention are particularly suitable go for steam turbines, reciprocal steam engines, general lubrication of machinery kept in the open, car journals, machinery in machine shops, textile machinery, home lubrication, etc. Also, the alkyl malonlc acids may be used in cutting oils, elec- 25 trical oils, Diesel 'fuels, gasolines, etc.

Moreover, the utility of the alkyl malonic acids is not restricted to hydrocarbon oils. They may be incorporated in various other stable and substantially neutral liquids, i. e., having dissociation constants below about 10- as various chlorinated hydrocarbons, e. g., propyl chloride, butyl chloride, ethylene dichloride, carbon tetrachloride, chlorinated kerosenes, etc.; esters, e. 55;, alkyl acetates, propionates, butyrates, lactates, stea rates, oleates; alkyl and aryl phosphates, thiophosphates, phosphites, etc.; sperm oil, fatty oils; very weak bases as pyridine, alkyl pyridine, quinolines, petroleum bases, etc. However, all of these liquids should be substantially free from resins, such as polymerized fatty oils, phenol formaldehyde resins, glyptal resins, etc. In hydrocarbon oils and other liquids of low dielectric constants which are not conducive to ionization of dissolved alkylates, the presence of small amount of less than 1% of one of the above polar liquids which is miscible therewith may considerably enhance thev activity of the alkyl malonic acids. Likewise, a small amount, less than 1% of a fatty or naphthenic acid of, say, 7-30 carbon atoms, has a 50 similar enhancing effect.

tilde of Liquids other than hydrocarbon oils containing the aglizlsmic acids are useful for a multisuch as coolants for internal combustion engines or various hydraulic applications as-in damping mechanisms, airplane landing gears, hydraulic brakes, etc.

Amounts of the alkyl malonic acids required to give positive corrosion'protection may be as low as 001%. In general, however, amounts between about .005% and .0596 are preferred.

The solubility of the alkyl malonic' acid in various hydrocarbon oils is quite low, it being only about .02% for the Clo-C20 alkyl malonic acids.

i above about 40 carbon atoms, although one may go as high as, say, 60 or even higher. If concentrations of the alkyl malonic acids above their solubility limit are desired, colloidal solutions may be resorted to. For many purposes, however, colloidal dispersions are objectionable because they tend to cause emulsification with water. Further, they may coagulate, causing the loss of at least a portion ofthe active agent. Hence in general and whenever possible, it is desirable to stay within the solubility limits of the acids.

Where desired and necessary, hydrocarbon compositions may contain various anti-oxidants such as alkyl phenols. aromatic amines, preferably secondary amines, amino phenols; as well as extreme pressure compounds, anti-wear com. pounds, detergents, sludge-preventing compounds, pour point reducers, thickeners, such as Oil Alkyl malonic acid Corrosion 150 s. U.-vis. at .oosaz cetyl malonic None.

. aci DoJ .do. Do. Do .0057, octyl ootyi ma- Do.

ionic ac Do 005% lauryl oetyl ma- Do.

Ionic acid. 300 S. U. vis. at 100 F .01% lauryl eetyl me- Do.

Ionic acid.

1 Sample of oil containing eetyl malonic acid was heated to 300 F. for several hours prior to test. Cetyl malonic acid by itself decomposes at 250 F.

' I claim as my invention:

A corrosion inhibiting turbine oil containing a corrosionretarding amount, from 0.001 to 0.1%

of an alkyl malonic acid having at least 16 carbon atoms, said turbine 011 being stable and retaining its corrosion inhibiting property at a temperature above the decomposition temperature of said alkyl malonic acid alone and at a temperature up to about 300 F.

FREDERICK T. WEISS. 

